摘要
REBa_(2)Cu_(3)O_(x)(REBCO)coated conductors exhibit irreversible critical current(I_(c))degradation under tensile strain beyond the irreversible strain(ε_(irr)).While this degradation is attributed to cracking,the specific crack evolution process and its quantitative relation to I_(c)degradation remain unclear.Here,the multiplication of cracks in REBCO tapes under tensile is characterized.It was found that surface particles disrupt continuous crack propagation,causing fragmentation of the REBCO layer.A shear lag model describes how the stress distribution evolves with fragmentation spacing.A probabilistic fracture model then predicts the two-regime spacing reduction as a function of applied strain.The discontinuous crack network acts as the residual flow channel for current once strain exceeds𝜀ε_(irr).Crack spacing determines the remaining I_(c)in this regime.An analytical model is thus proposed to capture the I_(c)degradation behavior based on the quantified fragmentation process.Additionally,this study suggests approaches to obtain a wider safe operating strain range through tailoring of the fracture behavior,expanding the practical application limits.This work provides new insights into the progressive cracking mechanisms governing irreversible I_(c)degradation in strained REBCO tapes.
基金
supported by the National Natural Science Foun-dation of China under Grant No.52407029,No.52277026,and No.12327901.
